Permafrost-Affected Rivers Can See an Increase in Runoff in a Warmer Climate, Even With the Same Amount of Precipitation
Observations show increases in river discharge to the Arctic Ocean especially in winter over the last decades but the physical mechanisms driving these changes are not yet fully understood. We hypothesize that even in the absence of a precipitation increase, permafrost degradation alone can lead to increased annual river runoff.
The simulations demonstrate that changes in permafrost characteristics due to climate warming and associated changes in evapotranspiration provide a plausible mechanism for the observed runoff increases in Arctic watersheds. This study shows that the changing water pathways (more water is going under the surface in a warmer climate) can be very important for surface moisture budgets with potential implications for droughts.
Observations show increases in river discharge to the Arctic Ocean especially in winter over the last decades but the physical mechanisms driving these changes are not yet fully understood. We hypothesize that even in the absence of a precipitation increase, permafrost degradation alone can lead to increased annual river runoff. To test this hypothesis we perform millennium-long simulations over an idealized hypothetical watershed using a distributed, physically based water balance model. The model is forced by both a hypothetical warming defined by an air temperature increase of 7.5 ∘C over 100 years and a corresponding cooling scenario. To assess model sensitivity we vary soil saturated hydraulic conductivity and lateral subsurface flow configuration. Under the warming scenario, changes in subsurface water transport due to ground temperature changes result in a 7%–14% increase in annual runoff accompanied by a 6%–20% decrease in evapotranspiration. The increase in runoff is most pronounced in winter.